This first image of a M79 Osa titled "One of JAN lions fighting to liberate Alsahweh brigade", taken from this Jabhat al-Nusra statement, comes from a joint operation with other opposition groups to capture a military base outside of Al Sahweh, Daraa that took place in the middle of February, and involved a number of groups using a large number of weapons provided by Saudi Arabia from Croatia in the battle.

The second image is taken from this report, and shows a M60 recoilless gun being used to attack an army outpost, Hajez Barad, in Busr al-Harir, Daraa, on March 2nd. From late December 2012 onwards Busr al-Harir has been the scene of heavy fighting when multiple opposition groups attacked Syrian army forces in the town using large numbers of the Croatian weapons provided by Saudi Arabia.

In both cases multiple opposition groups were involved with the fighting, many of which were the original intended recipients of these weapons, so it's possible that Jabhat al-Nusra received these weapons from those groups during the battles. It's unclear how many weapons they received, but it'll be another aspect of the Croatian arms story I'll be tracking in the coming weeks and months.